The tire vulcanizer includes an upper mold, a lower mold, and a bladder expanding and contracting under the supply/discharge of a heating gas (steam or the like), and is configured to press the bladder expanded by the supply of the steam, against the inner surface of a raw tire set inside the mold.
In such a situation, in order to eliminate the temperature difference within the bladder, a gas cycle apparatus arranged to circulate the heating gas is used, as set forth in, for example, Japanese Unexamined Patent Application Publication No. 62-33611.
As shown in FIG. 2, this gas cycle apparatus includes a bladder 1 expanding and contracting under the supply/discharge of a heating gas; a gas circulating flow path 2 constituted by allowing a forward flow path 2a connected to a supply port 10 of the bladder 1 and a return flow path 2b connected to a discharge port 11 of the bladder 1, to communicate with each other through a circulation valve 20; a gas feeder 21 (pump) provided in the gas circulating flow path 2; and a gas supply flow path 3 connected to the forward flow path 2a; and a gas discharge flow path 4 connected to the return flow path 2b. 
In a state where a gas supply valve 30 and gas discharge valve 40 are opened and the circulation valve 20 is closed, a heating gas is supplied from the gas supply flow path 3 to the inside of the bladder 1 to fill it with the heating gas. Thereafter, the gas supply valve 30 and gas discharge valve 40 are closed and the circulation valve 20 is opened. Under this situation, the heating gas is circulated between the gas circulating flow path 2 and the inside of the bladder 1 by the gas feeder 21.
However, in such a conventional gas cycle apparatus, a drain of the heating gas liquefied by a heat exchange within the bladder 1 undesirably flows in the gas circulating flow path 2.
When the drain of the heating gas flows in the gas circulating flow path 2, an excessive load is applied to the gas feeder 21 of the gas cycle apparatus, so that it becomes difficult to increase the circulation flow rate of the heating gas.
This has caused a, problem in that the temperature difference eliminating capacity in the bladder 1 decreases, and the tire vulcanizing time increases, resulting in the reduction in production capacity of tires.
The present invention has been made for solving the above-described conventional problem. For this purpose, an air-water separation section is provided in the gas circulating flow path, and the drain is stored in this air-water separation section, whereby the drain is prevented from flowing in the gas circulating flow path.
This inhibits an excessive load by the drain from being applied to the gas feeder of the gas cycle apparatus, and thereby increases circulating flow rate of the heating gas.
As a result, the temperature difference eliminating capacity in the bladder is improved and the tire vulcanizing time is shortened. Herewith, the present invention aims to provide a gas cycle apparatus for a tire vulcanizer, capable of enhancing the production capacity of tires.